The present invention relates to an apparatus for photographing CRT images on a plurality of frames of film.
Apparatus are used for photographing on more than one frame of a sheet of film, for example, sectional images of the human body projected on the screen of a CRT by X-ray diagnosis or ultrasonic diagnosis for therapeutic purposes.
The conventional photographic apparatus of this type include those having the construction shown in FIG. 10. A film 2 is spaced from the screen of a CRT 1 substantially in parallel therewith, and a plurality of lenses 3 corresponding in number to the number of frames of the film 2 are provided between the film 2 and the CRT 1 for projecting images on the CRT 1 onto the frames of the film 2. Shutters 4 provided in front of the lenses 3 are opened in succession to photograph images on the CRT 1 on the plurality of frames.
The conventional apparatus further include those having the construction shown in FIG. 11. A film 2 is spaced from the screen of a CRT 1 substantially in parallel therewith, and a single lens 3 is interposed between the film 2 and the CRT 1 with the optical axis of the lens positioned substantially perpendicular to the CRT screen and to the film 2. The combination of the CRT 1 and the lens 3, or the lens 3 only is moved in parallel with the film 2, or the film 2 is moved in parallel with the CRT 1 and the lens 3 which are fixed in position, to photograph images on the CRT 1 on a plurality of frames of the film 2 (e.g., Unexamined Japanese Patent Publication Nos. SHO 61-77827 and SHO 60-252332, and Unexamined Japanese Utility Model Publication No. SHO 59-25521).
With the arrangement of FIG. 10, the different lenses 3 are used for photographing images on the different frames of the film 2. Since the production of the lenses 3 involves errors, these errors appear as enlarged on the film 2, with the result that the degree of focusing or image density differs from frame to frame to produce visually recognizable differences in quality between the photographed images. Such differences could lead to a diagnostic error. Furthermore, the apparatus is costly since the plurality of lenses 3, as well as of shutters 4, are required in corresponding relation to the number of frames.
The arrangement of FIG. 11 affords images of high quality and is therefore used for apparatus of the sophisticated. However, the parallel movement of the lens 3 and the CRT 1 requires a linear motor, bearings, rails, etc., which render the apparatus complex in its entirety. Alternatively, the film 2 must be moved within a dark chamber, which also makes the apparatus very complex and costly to manufacture.